Nymaim

Overview

Nymaim is a sophisticated dual-stage malware downloader and loader first observed in 2013. Designed with extreme resilience, Nymaim specialized in evading security sandboxes and malware analysis environments by employing multi-layer encryption, dynamic API resolution, and timing-based anti-emulation routines before fetching its secondary payloads. Nymaim was one of the core malware families hosted and distributed on the bulletproof 'Avalanche' infrastructure network. In November 2016, an unprecedented joint operation led by Europol's European Cybercrime Centre (EC3), the US Attorney's Office for the Western District of Pennsylvania, the FBI, German Police (LKA Niedersachsen), and Eurojust dismantled the Avalanche infrastructure, seizing over 800,000 domains. Notably, Nymaim's stealth loader engine was combined with the banking webinject capabilities of Gozi (ISFB) to spawn 'GozNym'—a hybrid financial trojan that stole over $100 million from American and European businesses until its operators were indicted in US federal court in 2019.

Known aliases

Threat reports may refer to this family under multiple names:

• Nymaim
• Win32/Nymaim
• Trojan.Nymaim
• GozNym Precursor

Threat Actor Attribution

Attribution is probabilistic, not a science. Each link below states its confidence level and the evidence behind it.

• Avalanche Cybercrime Network / Europol EC3 & US DOJ Operation Avalanche High confidence
  Basis: November 2016 international takedown of the Avalanche bulletproof hosting infrastructure led by Europol, Eurojust, and the FBI, followed by the May 2019 US federal indictment of the GozNym syndicate that weaponized Nymaim code. [source]

Family Pedigree & Lineage

Malware authors regularly fork and iterate upon existing codebases. Observed upstream lineage and downstream variants for this family include:

Known Derivatives & Downstream Variants: Nymaim V1.0 · Nymaim Two-Stage Loader · Goznym (Hybridized With Gozi Isfb)

MITRE ATT&CK Techniques

Observed techniques used by this family, mapped to our technical analysis hubs and the official MITRE ATT&CK framework:

Tactical Mitigations

Based on the techniques used by this family, consider the following defensive strategies:

• T1071.001: Implement web filtering and SSL/TLS inspection to detect malicious command and control (C2) traffic hiding in HTTP/HTTPS.

MITRE D3FEND™ Defensive Countermeasures

Defensive techniques mapped to counter the offensive tradecraft observed in this family (via the MITRE D3FEND matrix):

Exploited Vulnerabilities (CVEs)

This malware family is documented weaponizing the following common vulnerabilities and exposures:

• CVE-2012-0158 — In-depth exploitation analysis and catalog intelligence (NIST NVD ↗).
• CVE-2014-1761 — In-depth exploitation analysis and catalog intelligence (NIST NVD ↗).
• CVE-2015-5119 — In-depth exploitation analysis and catalog intelligence (NIST NVD ↗).

Command & Control (C2) and Network Profile

How this family talks to its operators. C2 traffic can often identify a family even when its code and configuration are hard to analyse. Ports and patterns are historical and change between campaigns, so use them as hunting leads rather than block-only rules.

Indicators of Compromise

Public indicators drawn from CISA advisories and vendor reporting. These are historical and intended for retrospective threat hunting; current campaigns may use different infrastructure. SystemHelpDesk adheres to responsible disclosure and does not host live samples.

File hashes (SHA-256, sample)

Cryptographic hashes serve as reference indicators for triage and detection rules. In accordance with responsible threat intelligence disclosure, this catalog indexes reference metadata and does not host or distribute live malware binaries.

• 2efb6d17b5e4c6981cfda552553ca4be969796ff07a835a96aef71a2ec703ce5
• b1b4c330f89fa6d165f973e20e8b22a08846c4f09a5b3a8634860b0ec89c565d

Delivery vectors

• Phishing campaigns delivering weaponized Microsoft Word documents exploiting CVE-2012-0158 and CVE-2014-1761
• Drive-by downloads from compromised websites hosting exploit kits (Blackhole, Angler)

Persistence mechanisms

• Process injection into trusted Windows system binaries
• Registry Run keys and scheduled tasks executing hidden payloads in %LOCALAPPDATA%

Tiered Detection Rules (Cisco CAIRN Model)

Modern threat detection requires multi-layered rule engineering. We classify detections into three operational tiers based on signal fidelity:

rule MALWARE_WIN_NYMAIM_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Nymaim"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "nymaim" ascii wide nocase
        $s2 = "nymaim" ascii wide nocase
        $s3 = "win32/nymaim" ascii wide nocase
        $s4 = "trojan.nymaim" ascii wide nocase
        $s5 = "goznym precursor" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Nymaim (Downloader) Execution & Triage
id: 5fbcad4b-3484-5e9e-88d1-0ea4df48bf4f
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Nymaim malware family. Detects suspicious execution from temporary user
  directories with hidden window flags and background transfer utilities.
references:
- https://malware-families-catalog.systemhelpdesk.com/families/nymaim
- https://malware-families-catalog.systemhelpdesk.com/defensive/ransomware-protection
- https://malware-families-catalog.systemhelpdesk.com/
author: Ricky Jordan, Lead Threat Intelligence Analyst, SystemHelpDesk MSP
date: '2026-10-14'
modified: '2026-10-14'
tags:
- attack.downloader
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1055
- attack.t1497_001
- attack.t1071_001
- attack.t1568_002
- attack.t1547_001
logsource:
  category: process_creation
  product: windows
detection:
  selection_process:
    Image|endswith:
    - \cmd.exe
    - \powershell.exe
    - \cscript.exe
    - \wscript.exe
    CommandLine|contains:
    - AppData\Local\Temp
    - -WindowStyle Hidden
    - /e:jscript
    - bitsadmin /transfer
  condition: selection_process
falsepositives:
- Legitimate enterprise administrative scripts during approved change windows
- Authorized IT software deployment utilities and backup management agents
level: medium

rule MALWARE_WIN_NYMAIM_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Nymaim tradecraft"
        tier = "T3 - Attribution Fingerprint"
        confidence = "High (Confirmed Family Signature)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        // Core family identifier & heuristic payload signatures
        $attrib_str = "nymaim" ascii wide nocase
        $pe_magic = "MZ" ascii
        $net_marker = "http" ascii nocase
    condition:
        uint16(0) == 0x5a4d and ($attrib_str and $net_marker) and filesize < 15MB
}

Containment & Response Steps

Ordered checklist for responders. Adapt to your environment and engage professional support for active incidents.

1. Isolate the host from the network immediately to prevent Nymaim from successfully requesting and executing secondary, high-impact payloads (e.g., ransomware or banking trojans).
2. Inspect proxy and DNS telemetry to identify the download URLs and staging infrastructure contacted by Nymaim; block these indicators enterprise-wide.
3. Audit temporary directories (%TEMP%, %APPDATA%, C:\ProgramData\) to locate and quarantine secondary executables or DLLs dropped by Nymaim.
4. Purge startup registry keys and scheduled tasks established to re-attempt payload retrieval.

What to Avoid

Common mistakes during response to this family that can destroy evidence, spread the infection, or worsen recovery.

1. Do not assume the incident is resolved simply because an antivirus tool removed the initial Nymaim dropper; always verify that secondary payloads and persistence hooks have been eradicated.
2. Avoid logging in with Domain Admin or privileged credentials on a machine suspected of running Nymaim until memory triage is complete.
3. Do not delay host isolation; automated lateral movement and credential dumping can occur within minutes of initial execution.

References & External Analysis

• Europol Press Release - Avalanche Network Dismantled
• US Department of Justice WDPA - GozNym Hybrid Cybercrime Indictments
• MITRE ATT&CK - Nymaim
• Search "nymaim" on VirusTotal (External Analysis)
• Search "nymaim" on Any.Run (Sandbox Sandbox)
• Search "nymaim" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Downloader)

Explore other documented threats in the same operational category:

• Fraudrop
• Amonetize
• Tinyloader
• Upatre
• Tempedreve
• Nymeria
• Gepys
• Banload

Machine-readable

Get this profile as JSON: https://malware-families-catalog.systemhelpdesk.com/api/nymaim.json

Ecosystem & Interactive Environments

This profile is part of the Malware Families Catalog, a public dataset of 2,899 malware families. The catalog is also published across our ecosystem: Hugging Face, Kaggle, Zenodo, Replit, StackBlitz, CodeSandbox, and CodePen.